When I open up Metro Firefox and use a mouse, the left arrow button from the <arrowscrollbox> in the tab strip is visible and enabled, even if the box is not scrollable because there is only one tab. I suspect a regression from bug 936635.

Taking this for the current iteration; p=2.

We were setting "display: visible !important" on the left arrow in precise mode, which overrode the [collapsed] attribute set by the arrowscrollbox code. This patch instead just overrides the display to "hidden" when they would otherwise be collapsed.

Comment on attachment 8356599 [details] [diff] [review] patch Can you include an update the browser_tab_container.js test from bug 952663 to turn its todos() into is() and confirm the tests pass with this change?

The tests are now passing after some minor tweaks. I had to use a hard-coded timeout because the arrowscrollbox animated scrolling code uses the same hard-coded timeout. I'll file a follow-up bug and patch tomorrow to make arrowscrollbox fire an event we can listen to instead.

Comment on attachment 8357001 [details] [diff] [review] patch v2 Review of attachment 8357001 [details] [diff] [review]: ----------------------------------------------------------------- Looks good and works for me.

Comment on attachment 8357001 [details] [diff] [review] patch v2 [Approval Request Comment] Bug caused by (feature/regressing bug #): bug 936635 User impact if declined: Cosmetic glitch in Metro tab bar when using a mouse. Testing completed (on m-c, etc.): On m-c since 01-08, includes automated test. Risk to taking this patch (and alternatives if risky): Low-risk, Metro-only CSS change. String or IDL/UUID changes made by this patch: None.

For iteration #22, verified as fixed with latest Nightly and Aurora on Win 8.1 64-bit.